Study Of The Properties Of Mn-Doped GaAs Material

Diluted magnetic semiconductors (DMSs) are a new type of semiconductor material formed by substituting magnetic metal ion for nonmagnetic ion. DMSs have attracted a great deal of attention because of their potential application to spin-electronic device and quantum computer dull to their combined properties of both magnetic materials and semiconductors.At present, searching for DMSs with ferromagnetism at room temperature have become the hotspot of this field. It was reported that the secondary phase of MnAs has been found in GaAs substrate by Mn-implanted and subsequent rapid thermal annealing. MnAs shows ferromagnetism at room temperature and has a higher Curie temperature (318K). The magnetic properties of Mn-implanted GaAs have been studied more before, but the electrical properties and the form of Mn are not clear.In this paper, we implanted Mn+ ion of different dose into undoped semi-insulating (100) GaAs substrate then performed rapid thermal annealing in different temperature and time. Studied the different annealing condition dependence of the samples' structure, electrical and magnetic properties and the relation of the Mn+ forms and these properties. We also investigated the effect of C on the samples formed by ion implantation of Mn and C.We studied the samples' crystal structure and surface appearance by X-ray diffraction and AFM, experimental results revealed that with increasing the annealing temperature, the crystal lattice reformed and defect in the surface reduced gradually. One diffraction peak of the secondary phase was found in the XRD spectrum of sample annealing at 850℃ for 15s.We measured the samples' electrical properties (square resistance, square carrier concentration, carrier mobility and Hall coefficient) at room temperature by Hall measurement. The experimental results revealed that all the samples are P-type, with increasing the annealing temperature, the carrier mobility increased and the square carrier concentration decreased. These changes in electrical properties are explained by a decrease in the number of Mn acceptors because of the forming of MnAs phase and the resuming of lattice defects during annealing.Electrochemistry C-V method was employed to measure the carrier concentrationprofile distribution of samples, discovered that the carrier concentration decreased with increasing of the diffusion depth, and the peak of concentration located at 0.25μm beneath the surface. By SIMS method, we analyzed the profile distribution of Mn and C, found that increasing the annealing temperature is beneficial to the diffusion of Mn, but has no influence to C.MFM and SQUID measurements demonstrate that sub micron single-domain magnetic MnAs particles found in sample annealing at 850℃ for 15s show ferromagnetism at room temperature and have a high Curie temperature more than 300K.